When treating hair with chemical coloring agents, it has been found advantageous to encapsulate locks of hair after applying the coloring agent thereto while the coloring agent acts to change the appearance of the hair. Such encapsulation serves to maintain the agent in close proximity to the hair and prevents dripping of the agent onto surfaces where it is not wanted. Clear capsules that allow a user to view the coloring process are taught in U.S. Pat. No. 4,942,893. These capsules can be formed from embossed plastic sheet stock to have a male side and a female side, connected by a hinge so as to be folded and locked together to encapsulate a lock of hair placed therein.
UK Patent Application 2 203 645 A teaches a capsule device which is similar to that taught in the '893 patent, but which is provided with one or more channels to facilitate the spread of the treatment agent through the encapsulated space containing the lock of hair. Other devices for maintaining chemical agents on the hair employ a combination of a foam lining with a plastic shell, such as taught in U.S. Pat. No. 5,228,465. The '465 device employs reinforcing ribs to increase its rigidity, enabling the device to be suitable for straightening hair as well as for coloring operations.